The present invention relates to a method of developing a photosensitive (photographic) material comprising a layer containing a nondiffusible coupler and a nondiffusible color developing agent with a color developer containing a color developing agent comprising an aromatic primary amine, and thereby a dye image can be rapidly and stably formed.
An ordinary method of forming an image with a silver halide color photosensitive material comprises processing the silver halide photosensitive material with a color developer containing a color developing agent comprising an aromatic primary amine in the presence of a color coupler capable of reacting with an oxidation product of the developing agent to form a dye. Thus an azomethine dye or indoaniline dye is formed. This color developing method was first invented by L. D. Mannes & L. Godowsky in 1935. After improvement in various ways, this method is now employed through the world.
The method of processing the color photosensitive material basically comprises the following three steps:
(1) color developing step, PA0 (2) bleaching step, and PA0 (3) fixing step.
The bleaching and fixing can be conducted simultaneously in a bleach-fixing step (so-called blix step). In this step, developed silver and non-developed silver halide are removed by desilverization. In fact, the developing process includes various auxiliary steps to maintain the photographic and physical qualities of the image and to improve the shelf stability of the image, in addition of the two basic steps, i.e. color developing step and desilverization step. Baths usable in this process include, for example, a hardening bath for preventing an excess softening of the photosensitive layer in the course of the process, stop bath for effectively stopping the developing reaction, an image-stabilizing bath for stabilizing the image and a bath for removing a packing layer from the support.
A color developer used in the color developing step is a solution of a color developing agent comprising an aromatic primary amine in an aqueous alkali solution. The aromatic primary amine color developing agent penetrates into the photosensitive layer to develop (or, in other words, to reduce) the exposed silver halide. On the contrary, the developing agent is oxidized by the silver halide to form an oxidation product. The oxidized developing agent is diffused in the gelatin layer and coupled with a coupler previously dispersed therein by an oil protecting method to form a dye.
The order to prevent environmental pollution, a color developer that is free from benzyl alcohol is used mainly nowadays. However, when the benzyl alcohol-free color developer is used, the sensitivity is reduced and the maximum color density (D.sub.max) is also reduced. Further for obtaining a photosensitive material which yields an image of a high quality and a high sharpness, the thickness of the emulsion layer is reduced to reduce fuzziness by light scattering. In one of the techniques of this method, the ratio of an oil in which the coupler is dispersed to the coupler is lowered. When the ratio of the oil to the coupler is lowered, D.sub.max is reduced as in the case of using benzyl alcohol-free solution.
In one known method for solving the problem that the developing activity is reduced and thus so is the rapidness, the pH of the color developer is increased and the processing temperature is elevated to accelerate the development. However, this method has serious problems in that fogging is serious, the developer becomes unstable and the photographic properties become variable in continuous processing. Another proposed method comprises using various development accelerators, but the acceleration effect of these is not yet satisfactory.
Through their studies, the inventors have found that a color developing agent is distributed into the oil which disperses the coupler in the gelatin layer and that the amount of the distributed color developing agent varies depending on the kind of the coupler and the dielectric constant of the oil. The inventors have found also that as the amount of the color developing agent distributed into the oil is increased, the color development rate of the sensitive material is increased. Namely, the higher the density of the color developing agent in the oil, the higher the dye forming rate of the material. After further investigations, the inventors have found that the dye forming rate is effectively increased by adding a nondiffusible color developing agent to the oil beforehand.
On the basis of these findings, the inventors have succeeded in formulating a photosensitive material which makes it possible to rapidly form dye with only a slight processing dependence in the development with a color developer. Namely, the photosensitive material contains a nondiffusible color developing agent together with a coupler.
Many methods are known for developing a photosensitive material containing a color developing agent with an aqueous alkali solution.
For example, U.S. Pat. No. 3,342,599 discloses the use of a Schiff base with salicyl aldehyde as a precursor of the developing agent. U.S. Pat. No. 3,719,492 discloses the use of a metal salt such as lead or cadmium salt. British Patent No. 1,069,061 discloses a precursor of a phthalimide type prepared by reacting an aromatic primary amine with phthalic acid. Japanese Patent Application No. 52-26756 discloses the use of a combination of an aromatic primary amine with a cyclic .beta.-dicarbonyl compound. Japanese Patent Application No. 52-50909 discloses the use of a precursor prepared by bonding an aromatic primary amine with a substitued or unsubstitued (2-benzenesulfonyl)ethoxycarbonyl. Other methods are disclosed in, for example, German Patent Nos. 1,159,758 and 1,200,675, U.S. Pat. No. 3,705,035Japanese Patent Unexamined Published Application (hereinafter referred to as `J. P. KOKAI`) Nos. 57-14838 and 57-14839, and Japanese Patent Publication for Opposition Purpose (hereinafter referred to as `J. P. KOKOKU`) Nos. 63-16730 and 63-18732.
For developing a silver halide color photosensitive material containing the color developing agent or its precursor, there is used an alkaline aqueous solution having a pH higher than that of a conventional developer in order to decompose the precursor into the color developing agent and to increase the velocity of the reduction of a silver halide into metallic silver as compared with the velosity of the dissolution of the color developing agent or its precursor in the alkaline aqueous solution. The most suitable pH, which varies depending on the combination of the color coupler and the color developing agent or its precursor, is usually in the range of about 10 to 14, preferably 11 to 13.
However, when the alkaline aqueous solution having such a high pH is used for the processing, its pH is lowered by, for example, carbon dioxide in the air or hydrogen ions produced in the photosensitive material as the color development proceeds. Thus it is quite difficult to stably keep such a high pH of the alkaline aqueous solution. When the pH of the alkaline processing solution is lowered, the development rate of the photosensitive material is seriously reduced and, particularly in the continuous process, the quality of the finished product is not uniform and the maximum color density is reduced.
When the photosensitive material contains a precursor of the color developing agent, the precursor must be first activated with an alkaline aqueous solution. Therefore, it takes a long time for the color development. This is disadvantageous from the viewpoint of acceleration of the process.
Because of these problems, the photosensitive material containing the color developing agent or its precursor has not yet come into practical use.
The present invention is characterized in that a photosensitive material containing a nondiffusible coupler and a nondiffusible color developing agent is processed with a color developer containing an ordinary color developing agent comprising an aromatic primary amine. Therefore, the pH of the developer can be within an ordinary pH range (9 to 12) and it has no problem regarding stability. Further since the nondiffusible color developing agent is directly contained in the photosensitive material in the present invention, the step of the activation of the precursor of the color developing agent as described above is unnecessary. This is advantageous from the viewpoint of rapid processing.
U.S. Pat. No. 4,297,437 discloses an invention wherein a photosensitive material containing a developing agent and/or its precursor is continuously color-developed while a color developing replenisher containing a color developing agent is fed in such a manner that the amount of the color developing agent replenished is minimized. In this invention, the color developing agent contained in the photosensitive material must be diffusible, since it must be diffused into the developer so as to replenish the color developing agent in the developer.
On the contrary, the color developing agent contained in the photosensitive material of the present invention is preferably not diffused into the processing solution. When a diffusible color developing agent which diffuses into the solution is used, problems such as reduction of the maximum color density, increase of variation of the photographic properties in the cource of continuous processing and reduction of the stability of the developer arise. Therefore, the present invention is completed by incorporating a nondiffusible color developing agent which does not diffuse into the developer in the developing step in an oil containing a nondiffusible coupler.
J. P. KOKAI Nos. 62-178962 and 62-178963 disclose a photosensitive material having excellent fastness to light by incorporating a p-phenylenediamine compound therein together with a cyan coupler. However, an unsubstituted amino group is not required of the p-phenylenediamine compounds used in these inventions, since they are used as a photo-fading inhibitor for the cyan coupler. Namely, it is not required of them to exhibit the coupling activity upon oxidation.
On the other hand, the nondiffusible color developing agent is contained in the oil together with the nondiffusible coupler so as to accelerate the color development, and its oxidation product must have a coupling activity with the coupler in the present invention. Thus the above-described two inventions are utterly different from the present invention.